5-oxopent-3-ene-1,2,5-tricarboxylate decarboxylase; 5-carboxymethyl-2-oxo-hex-3-ene-1,6-dioate decarboxylase; 5-oxopent-3-ene-1,2,5-tricarboxylate carboxy-lyase; 5-oxopent-3-ene-1,2,5-tricarboxylate carboxy-lyase (2-oxohept-3-enedioate-forming)